1. Field of the Invention
The present invention generally relates to demodulators for communication systems and, more particularly, to a new non-coherent demodulator for a digital communication system which exhibits superior performance in a fading channel.
2. Description of the Prior Art
The modulation scheme for the Cellular Digital Packet Data (CDPD) system is Gaussian filtered Minimum Shift Keying (GMSK) with modulation index 0.5. There are several demodulation structures for GMSK such as a Frequency Modulation (FM) discriminator, coherent demodulation and differential demodulation. Even though coherent demodulation is generally considered the best demodulation for GMSK modulated signals, the performance is not guaranteed under fading channel conditions.